In recent years, multi-jet fusion technology became more popular as it has unlimited potential. Thanks to this technology, it became possible to produce products with complex geometries.This gives a massive advantage compared to the conventional manufacturing process, as by utilising 3D printers, the costs and environmental impact are reduced exponentially with regards to the fact that this is a new technology. Product quality is one of the most important factors when it comes to product manufacturing for a company to stay competitive in the market. This study was conducted in FABLAB at Halmstad University. The research focuses on different aspects of the fabricated test artefacts, such as surface roughness, tensile strength and dimensional deviation. How different printing parameters can affect the printing quality of the printed parts is then analysed. The result is then compared with designed CAD model. During this study, some experiments were conducted by printing test samples at different build orientations to define the printing quality. Measurement is conducted on the different test artefacts and quantified. The effect from build orientation on surface roughness, tensile strength and dimension accuracy were studied during this thesis. The test samples were measured by using appropriate measuring equipment that was available at Halmstad University. From the test results, it becomes clear that the build orientation directly impacts the printing quality of the printed test samples from the HP multi-jet fusion 3D printer

The appearance and design of a package are key properties to attract and to focus the attention of a customer. Print quality contributes to a great degree to achieve these requirements. Most critical perceived in terms of quality are print defects like mottling, gloss and stripiness, which all appear in the printing of corrugated board. Stripiness is especially critical because it is a defect directly caused by the corrugated board construction. A further cause can be generated by the production process of corrugated board. Pre-studies by Odeberg Glasenapp (2004) revealed a difference in surface micro-roughness between the regions on the peak line of the liner and the regions in the valley between two peaks of the corrugation. This knowledge was the basis for the work described in this thesis. In a first stage, laboratory trials were conducted with sets of coated and uncoated samples of various grammages. The trial was set-up in order to simulate the conditions in the corrugator as closely as possible. In the evaluations, it was found out that the settings were too high. For that reason, the coated samples were influenced to a too high degree and needed to be excluded from further evaluations. With the uncoated samples, on the other hand, a change in micro surface roughness was detectable. The roughness is decreased on the peaks and the gloss appearance was the conclusion. The analysis of the printed samples focused on shifts in colour and print density. It is unclear if both are affected only surface roughness changes and/or by the typical corrugated board effect of washboarding. A full-scale test was performed in order to confirm the results of the laboratory test. A test series was chosen with coated and uncoated outer liners. Contrary to the lab-test results, the uncoated grades showed no surface roughness changes. Instead, the coated samples were affected to a great extent. The changes in surface roughness and gloss appearance were similar to the lab-test. This confirms that the lab-test samples were exposed to heat, pressure and shear to a too high degree. The print analysis of the full-scale test did not agree with the laboratory test. Gloss lines were visually detectable, but they were difficult to measure. A reason could be that the ink is capable on forming an ink film layer on top of the surface of the paper. This would cover the micro roughness of the matt parts thereby creating an almost homogeneous glossy appearance. / QC 20101116

Tracking and tracing are a key technology for production process optimization and subsequent cost reduction. However, several industrial environments (e.g. high temperatures in metal processing) are challenging for most part-marking and identification approaches. A method for printing individual part markings on metal components (e.g. data matrix codes (DMCs) or similar identifiers) with high temperatures and chemical resistance has been developed based on drop-on-demand (DOD) print technology and special ink dispersions with submicrometer-sized ceramic and glass particles. Both ink and printer are required to work highly reliably without nozzle clogging or other failures to prevent interruptions of the production process in which the printing technology is used. This is especially challenging for the pigmented inks applied here. To perform long-term tests with different ink formulations and to assess print quality over time, we set up a test bench for inkjet printing systems. We present a novel approach for monitoring the printhead’s state as well as the print-quality degradation. This method does not require measuring and monitoring, e.g. electrical components or drop flight, as it is done in the state of the art and instead uses only the printed result. By digitally quantifying selected quality factors within the printed result and evaluating their progression over time, several non-stationary measurands were identified. Some of these measurands show a monotonic trend and, hence, can be used to measure print-quality degradation. These results are a promising basis for automated printing system maintenance.

Large Scale Additive Manufacturing (LSAM) technology has emerged as a transformative force in the manufacturing industry. Using robots and advanced material deposition systems, LSAM facilitates the efficient creation of large-scale components with exceptional precision and reduced production times. Beyond its capacity to manufacture complex structures, this technology drives innovation by fostering the exploration of new materials and designs, opening new frontiers in the aerospace, automotive, and construction sectors. The synergy between robotics and additive manufacturing in LSAM represents a significant advancement toward the future of manufacturing, where customization, efficiency, and sustainability are paramount.  Within the framework of this research, conducted in collaboration with ABB and RISE, a series of tests have been developed to optimize printing parameters when transitioning from one material to another. This study showcases how simple adjustments in the workflow of robotic stations can lead to significant improvements in print quality and increased resource efficiency, paving the way for more precise and sustainable manufacturing.  This research has not only generated valuable insights into the behavior of LSAM under different operating conditions but also provided practical solutions for its continuous improvement. These findings are relevant for the continuous improvement of large-scale additive manufacturing processes and provide important insights for future research in the fields of robotics and advanced manufacturing. Additionally, a systematic methodology has been developed to evaluate and validate results, ensuring the reliability and reproducibility of findings. These achievements solidify the role of LSAM as a fundamental technology in the evolution of the manufacturing industry toward a more efficient and sustainable future.

This thesis treats static and dynamic surface characterization using radiometric and Fourier optical methods. A Fourier optical method has been developed for real time image processing in paper production and printing applications. It has been shown that the method can be used to measure crepe frequency, an important parameter in tissue paper production, as well as to monitor the wire mark pattern at paper web velocities of up to 20 m/s. The wire mark pattern has been used to measure dimensional variations across a paper web. These are important for the mechanical properties of paper. Imaging of the moving surfaces onto a spatial light modulator, necessary for Fourier optical analysis of opaque objects, constitutes a motion blur problem. This problem has been solved by means of optical motion compensation using a rotating mirror. A rotating mirror system has also been developed for the inspection of small particles fixed to a rotating sample disc. The optical motion compensation configurations have made exposure times of more than two orders of magnitude longer than the exposure time without compensation possible. A light scattering model for opaque objects, for example coated paper, has also been developed and verified, with a coefficient of determination between theory and measurement ranging from r2=0.84 to r2=0.98, on various paper samples. The light scattering model has been used in the development of an instrument based on the photometric stereo principle. In this instrument the reflectance (or color) and topography of opaque samples are determined from two or more images of the sample illuminated from different directions. The method has been successfully used for studies of the relation between topography and print results in gravure and flexographic printing. Comparisons of surface height profiles measured with the photometric stereo method and profiles obtained with mechanical and optical scanning stylus instruments have shown coefficients of determination of up to r2=0.97. The main advantages of the method are the high speed, the scalability and the ability to obtain reflectance and surface height maps of a surface simultaneously.

L'impression, bien qu'étant une technique ancienne pour la coloration de surfaces, a connu un progrès considérable ces dernières années essentiellement grâce à la révolution du numérique. Les professionnels souhaitant remplir les exigences en termes de qualité du rendu visuel de leurs clients veulent donc savoir dans quelle mesure des observateurs humains sont sensibles à la dégradation d'une image. De telles questions concernant la qualité perçue d'une image reproduite peuvent être séparées en deux sujets différents: La qualité de l'impression, comme la capacité d'un système d'impression à reproduire fidèlement l'image d'origine, et la qualité d'une image imprimée, résultant à la fois de la qualité de reproduction, mais aussi de la qualité même de l'image numérique d'origine. Ce premier concept repose sur une analyse physique de la façon dont l'image d'origine est dégradée lors de son transfert sur un support, et nous proposons de la coupler avec une analyse sensorielle, visant à évaluer des attributs perceptuels et leur donner une valeur sur une certaine échelle, déterminée par des échantillons de référence classés par un ensemble d'observateurs. Le second concept inclut cette dégradation due à l’impression mais aussi la qualité perçu de l’image d’origine, qui ne fait pas parti de notre étude. Notre approche consiste d'abord à définir les différents indices de qualité, basés sur des critères mesurables en utilisant des outils d'évaluation basés sur des algorithmes "objectifs" de traitement d'image et des modèles optiques, sur une image imprimée-scannée. Thèse réalisée au Laboratoire Hubert Curien / Printing, though an old technique for surface coloration, considerably progressed these last decades especially thanks to the digital revolution. Professionals who want to meet the demands in terms of quality regarding the visual rendering of their clients thus want to know to which extent human observers are sensitive to the degradation of an image. Such questions regarding the perceived quality of a reproduced image can be split into two different topics: the printing quality as capacity of a printing system of accurately reproduce an original digital image, and the printed image quality which results from both the reproduction quality and the quality of the original image itself. The first concept relies on physical analysis of the way the original image is deteriorated when transferred onto the support, and we propose to couple it with a sensorial analysis, which aims at assessing perceptual attributes by giving them a value on a certain scale, determined with respect to reference samples classified by a set of observers. The second concept includes the degradation due to the printing plus the perceived quality of the original image, not in the scope of this work. In this report, we focus on the printing quality concept. Our approach first consists in the definition of several printing quality indices, based on measurable criteria using assessment tools based on “objective” image processing algorithms and optical models on a printed-then-scanned image. PhD work made in Hubert Curien Laboratory